i. Typical Balloon Catheter and Procedures
Various types of balloon catheters are utilized in modern clinical medicine. Balloon catheters designed for transluminal angioplasty procedures usually incorporate a single dilation balloon formed on an outer surface of the catheter. The dilation balloon is sized and configured such that inflation of the balloon will effect dilation of an obstructive lesion within a blood vessel or other anatomical passageway. Balloon dilation angioplasty has become a widely accepted method of treating obstructions of the coronary and/or peripheral arteries.
A typical balloon angioplasty catheter comprises an elongate pliable catheter body having a proximal end, a distal end and at least one working lumen extending longitudinally through the catheter body to facilitate infusion of radiographic contrast media or other fluids. An inflatable dilation balloon is mounted on the outer surface of the catheter body, near the distal end thereof. A balloon inflation tube or lumen extends through the catheter body, from a balloon inflation port on the proximal end of the catheter, to the dilation balloon. The working lumen of the catheter may serve as a guide wire passage lumen, or a separate guide wire lumen may be provided apart from the working lumen through which fluids are infused. The guide wire lumen may extend through all, or a portion, of the catheter body to facilitate advancement of the balloon catheter over a prepositioned guide wire. Depending on whether the guide wire lumen extends through all or just a portion of the length of the catheter may be classified as a "monorail" catheter. Further descriptions of the typical "monorail" and "over-the-wire" catheter are as follows:
i. Monorail Catheters
In a "monorail" style catheter, a guide wire lumen extends through only a distal portion of the catheter, typically from a distal tip aperture to a proximal aperture formed in the side wall of the catheter body. Accordingly, as the catheter is advanced over the prepositioned guide wire, the proximal end of the guide wire will emerge from the side wall aperture such that the proximal portion of the guide wire remains outside of the catheter body as the catheter is advanced to its desired operative site. If it becomes necessary or desirable to exchange the balloon dilation catheter, the proximally exposed portion of the guide wire can be manually held and stabilized by the operator while the first catheter is removed and a second catheter is slid over the pre-positioned guide wire. Since the length of the catheter that must be passed over the guide wire is lessened in the "monorail" type of arrangement, it is typically easier for the operator to manually stabilize the guide wire during the exchange procedure and the need for a proximal extension or excessively long guide wire is eliminated.
ii. Over-the-Wire Catheters
The "over-the-wire" style of angioplasty catheter incorporates, a guide wire lumen which extends substantially through the entire length of the catheter. The guide wire lumen is separate from the balloon inflation lumen.
iii. Typical PTCA Procedure
In a typical percutaneous transluminal coronary angioplasty (PTCA) procedure a separate guiding catheter is initially inserted into a femoral artery or other peripheral artery. The guiding catheter is then advanced through the aorta to a position whereat the distal end of the guiding catheter is located adjacent or within the ostium of the coronary to be entered. Thereafter, an over-the-wire guide wire is inserted into the lumen of a balloon dilation catheter, and both wire and balloon catheter are advanced through the lumen of the guiding catheter. Thereafter, the guide wire is advanced into the obstructed coronary artery to a point where the distal end of the guide wire extends through the obstructive lesion. Thereafter, the balloon dilation catheter is advanced over the guide wire to a point where the dilation balloon is positioned within the obstructive lesion. Thereafter, the dilation balloon is inflated one or more times to dilate of the obstructive lesion, thereby relieving the obstruction of the coronary artery. After the lesion has been dilated, the dilation balloon is fully deflated and the balloon catheter, guiding catheter and guide wire are removed.
iv. Methods of Manufacturing Balloon Catheters
It is desirable that balloon dilation catheters, especially those of the type utilized for the above-described PTCA procedures, be constructed such that the dilation balloon is sufficiently strong to exert the required dilatory pressure against the offending lesion without causing rupture or disruption of the balloon. Also, because such balloon catheters are typically disposable items which are not intended to be reused, it is desirable that such catheters be manufactured as economically as possible to limit the expense associated with their clinical use.
The prior art has included methods for manufacturing balloon dilation catheters whereby the proximal and distal ends of the dilation balloon are affixed or bonded to the outer surface of a flexible cardiovascular catheter. However, such affixation or bonding of the balloon to the catheter typically results in the formation of seams or fusions which could fail or rupture during use.
There remains a need in the art for the development of new methods for manufacturing balloon catheters to eliminate the existence of catheter-balloon seams or fusions which could be subject to failure or leakage.